* {
    margin: 0;
    padding: 0;
}
.container {
    display: flex;
    justify-content: center;
    align-items: center;
    // 让子元素垂直排列
    flex-direction: column;
    /* 100%窗口宽度、高度 */
    width: 100vw;
    height: 100vh;
    background: radial-gradient(circle at center, #555, #000);
}
.container a {
    position: relative;
    display: block;
    width: 140px;
    height: 60px;
    line-height: 60px;
    text-align: center;
    margin: 40px;
    color: plum;
    text-decoration: none;
    font-size: 20px;
    transition: all 0.3s ease-in-out;
    // $colors: 1, 2, 3, 4, 5;
    // @each $c in $colors {
    //     &:nth-child(#{$c}) {
    //         filter: hue-rotate(calc($c * 60deg));
    //     }
    // }
    // 用sass的遍历法进行遍历，简单易懂了兄弟
    @for $i from 1 through 5 {
        &:nth-child(#{$i}) {
            filter: hue-rotate(calc($i * 60deg));
        }
    }
    &::before,
    &::after {
        content: '';
        position: absolute;
        width: 20px;
        height: 20px;
        border: 2px solid plum;
        // 最后的0.3s是延迟时间
        transition: all 0.3s ease-in-out 0.3s;
    }
    &::before {
        top: 0;
        left: 0;
        border-right: 0;
        border-bottom: 0;
    }
    &::after {
        bottom: 0;
        right: 0;
        border-left: 0;
        border-top: 0;
    }
    &:hover {
        background-color: plum;
        color: #000;
        box-shadow: 0 0 50px plum;
        // 倒影 below是下倒影
        -webkit-box-reflect: below 1px linear-gradient(transparent, rgba(0, 0, 0, 0.3));
        &::before,
        &::after {
            width: 138px;
            height: 58px;
            transition-delay: 0s;
        }
        transition-delay: 0.4s;
    }
}
